The present invention is related to optical networks in general and, in particular, to receiver/transponders with variable bit transfer rate digital filters.
A present trend in telecommunications is the installation of optical networks with ever increasing data transfer rates. Optical networks in general allow high signal bandwidths, and multiple communications channels can be created over a single optical fiber with techniques, such as WDM (Wavelength Division Multiplexing) and its successor DWDM (Dense Wavelength Division Multiplexing). Current and proposed optical networks offer bandwidths of 10, 40, and even 100 Gbs (Gigabits per second). This rise in bit transfer rates is a consequence of not only technical development but also the burgeoning demand for the much anticipated applications of voice, computer data and video delivery with optical networks. For example, such applications include video-on-demand, such as Internet TV, amateur video blogs, and social networking video.
The current enthusiasm for ever-increasing optical performance overlooks a potential problem. The eventual aging and inevitable deterioration in performance of these networks have not been considered to any extent. Of course, one way of dealing with a declining network is to simply replace it. But this is a very expensive investment and a time-consuming operation.
An alternative is to keep the declining network in operation. In optical network design, the quality of performance is balanced against the costs of such performance as in any actual system. That is, among other considerations, the links of a network are designed with a particular bandwidth in mind. The definition or the shape of an optical signal naturally deteriorates as the signal travels along an optical fiber and as the bandwidth, i.e., the bit transfer rate rises, the definition of the optical signal deteriorates faster. Thus the network, depending upon the signal bandwidth, must place optical amplifiers at locations along the link to regenerate the signals before they deteriorate beyond recognition. As network components age, optical performance naturally falls. Steps must be taken to ensure that the network operates at its maximum capacity despite the declining performance.
The present invention is directed toward adapting optical networks for declining optical performance.